North Sudan seizes disputed Abyei, thousands flee
Escalating tensions over oil region bring north and south to brink of conflict
North Sudan takes control of key town in Abyei
The oil-rich and fertile region is disputed by the north and south
South Sudan reports new northern attack in Abyei
The oil-producing region is an obstacle as the South heads to independence
North, south Sudan trade blame over Abyei attacks
Retaliation threat raises prospect of more violence in disputed oil-producing border region